The volume of data stored by organizations is thought to be growing geometrically. By some estimates, the digital data generated in a year exceeds the volume digital data generated in all previous years since digital data first began being generated. However, some of this data is rarely, if ever, accessed. Nevertheless, this data must remain accessible, e.g., for legal reasons. This rarely accessed data can be classified as “cold data.” Cold data is increasingly stored in cost-efficient storage systems (“cold data storage systems”).
Cold data storage has become an important market segment in the data storage field. The capacity of cold data storage systems is increasing. “Big data technology,” which is developing at a fast pace, requires a tremendous amount of cheap and massive storage space. It is predicted that by the year 2018, the total amount of data for the entire human world will reach a size of 44 zettabytes (ZB; 1 ZB=1 million petabytes (PB)). However, not all data will be stored and preserved at the same level of access. For example, the majority of the data being processed by the big data technology will be stored in the cold data storage, which is not immediately available to the processing system of the big data technology.
Organizations typically have various data retention policies. Most policies require data to be permanently deleted after expiry of various time periods. However, the data sometimes must be held longer and deleting it early may cause the organizations to incur various liability, e.g., because of “legal holds.” A legal hold order sometimes occur by order of a court of law, e.g., during a litigation. Organizations thus must take various precautions to ensure that they comply with both data retention policies and legal hold requirements.